Paying for contracts that I cannot use

I have been a customer of Vodacom for the past 18 years and find it unacceptable that I pay over R2000pm on my contracts with them and receive such shocking service. I have had signal issues at my home office since June last year and every time I complain nothing gets done. I am locked into contracts that I cannot cancel and have such poor service. I have been pushed from pillar to post trying to get some sort of feedback and never receive a suitable response. The last feedback I received was in Dec and the lady informed me that there is no solution and I'll just have to wait. I would really like some sort of feedback on this as my business is suffering in the interim.